Description: Transport and distribution of organic and biological compounds in unsaturated porous media depend on the chemical and physical properties of the media, the fluid and gas properties, and the characteristics of these substances. Because of the complexity of the transport processes in natural soils, needs exist to study these properties in experimental settings that closely mimic the natural complexities. On the other hand, it is often necessary to simplify the experimental setups to isolate single transport mechanisms of interest. In the proposed study, they intend to design and develop an intermediate- scale core facility to study flow and transport in variably-saturated soils. The laboratory will consist of two parts: a 1-m column and a 2 x 1 m sandbox. Both will be made of stainless steel and teflon and will be instrumented to monitor moisture content distributions, gas and fluid pressure and will have access ports for gas and liquid sampling. The column and the sandbox will be used to study 1-D and 2-D flow and transport of biological and organic compounds under well-controlled saturated or unsaturated conditions. In addition, the sandbox will permit studies of the effects of physical and chemical soil heterogeneities, such as lenses and layers, on unsaturated flow and transport. The facility will be available to all University of Arizona superfund research groups and it is currently anticipated that it will be used by at least three of the proposed superfund projects.